When drilling a wellbore, the drill bit may be turned by a rotation of the drill string or by a downhole motor. The downhole motor may be used to rotate the drill bit while the drill string is stationary. In such a drill string, the bottom hole assembly (BHA), located at the end of the drill string, may include the downhole motor, the drill bit, and a bearing section. The bearing section couples between the motor sub and the drill bit and houses the drive shaft which couples between the drill bit and the downhole motor. The bearing section couples to the drive shaft through one or more bearings to allow rotation of the drive shaft as the bearing section remains generally stationary within the wellbore.
During a directional drilling operation, a bent sub having an adjustable or fixed bend is typically included in the BHA between the downhole motor and the bearing section. The bent sub introduces an angle in the progression of the wellbore by angling the bearing section and therefore the drill bit relative to the downhole motor. However, the introduced external angle may, for example and without limitation, limit the ability to operate the drill string in rotary mode because of the increased bit orbit diameter, increased friction, and increased vibration or shock on the drill string.